1. Field of the Invention
The present invention relates generally to scanners and scanning methods, and more particularly to those permitting capture of image of an original positioned on the imaging surface that is illuminated by light sources that illuminate the corner areas of the imaging surface more brightly than the non-corner areas of the imaging surface.
2. Description of the Related Art
Scanning devices are used in a variety of applications. Scanning devices may be combined in an all-in-one unit that includes scanning, printing, and facsimile functions or may each be used independently. A conventional scanning device has an illumination system to illuminate the original that is to be scanned and an imaging unit for capturing the image of the illuminated original.
Often it is advantageous to reduce the size of the scanning device. One way of reducing the size of the scanning device is by placing the imaging unit of the imaging device close to the imaging surface. However, as a lens of the imaging unit gets closer to the imaging surface, the light from the outer edges of the imaging surface has significantly farther to travel to reach the lens of the imaging unit compared to the light from a non-corner portion of the imaging surface. This causes the image of original positioned near the corner portion of the imaging surface to appear less illuminated compared to the image of original positioned near the non-corner portion of the imaging surface. This is referred to as vignetting or roll-off effect that causes the corner of the original to seem darker than the rest of the original.
Therefore, it would be advantageous to have a scanning device that captures an image devoid of any undesirable darkness at the edges, thereby addressing the problem of vignetting and providing an output image with improved quality.